The invention relates generally to semiconducting materials and more specifically concerns a method for determining the point of zero zeta potential (pzzp), also known as the potential of zero charge (pzc) for an unpowdered semiconducting material.
In the past, two methods have been used to determine the pzc of semiconducting materials. Both methods require that the material be in powdered form. One method monitors the pH of a noncorrosive solution into which the powdered material is introduced. The pzc is determined at the point where no further change in solution pH is observed when additional powder is added. The other method involves the potentiometric addition of a known quantity of acid or base to a suspension of powdered material. From the observed changes in solution pH, the pH.sub.pzc can be calculated. A review of these methods and results can be found in Oxides and Oxide Films, vol. 2, J. W. Diggle, ed., Marcel Dekker, 1973, p. 281. The first method discussed above has been applied to determine the pH.sub.pzc of semiconductor electrodes used in photoelectrochemical cells and is discussed in Butler, M. A.; and Ginley, D. S.: Journal of Electro-Chemical Society, vol. 125, 1978, pp. 228 and 1968.
These methods require that samples of semiconductor materials be in the form of fine powder with a resulting large surface area capable of causing detectable changes in solution pH. This requirement results in the determination of the pH.sub.pzc of the material in a configuration in which it may not normally be utilized and also this value may not be correct for the material in unpowdered form.
The primary object of this invention is to provide a simple method that can be used to determine the pH.sub.pzc for nonpowdered semiconductor materials. Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.